It has long been known that polyethylene terephthalate (PET) has superior physical properties, e.g., resistance to chemical attack, and desirable mechanical and electrical properties. Despite these superior physical properties, PET is not always the material of choice for injection molding usage because relatively high mold temperatures, e.g., 120.degree.-140.degree. C., must be utilized to insure good moldability. Any attempt to use a lower mold temperature, e.g., 100.degree. C. or lower, results in the injected material being unmoldable as, for one thing, the molded article sticks in the mold and often can only be removed with great difficulty. To circumvent this processing disadvantage, the molder is forced to select more expensive materials such as polybutylene terephthalate (PBT), inasmuch as this poly(alkylene terephthalate) is easily moldable even when using mold temperatures as low as 60.degree. C. By being able to use a lower mold temperature for PBT, the time necessary for cooling the injection molded article to a temperature at which it can be removed from the mold is considerably shorter than the cooling time necessary before the PET article can be removed from a mold at 120.degree. to 140.degree. C. Since this shorter cool-down period of PBT results in a shorter process cycle time and a higher rate of article production, economic justification exists for its use despite its higher unit cost.
A welcome contribution to the art would be a PET composition which can be injection molded at relatively low mold temperatures (e.g., 100.degree. C. and below) to yield articles exhibiting improved moldability characteristics, e.g., improved mold releasability and desirable physical properties.
Copending application Ser. No. 294,980, filed Aug. 21, 1981 describes thermoplastic injection moldable compositions composed of a polyethylene terephthalate, a hydrocarbyl ester of a monoepoxidized alkenoic acid, and an adjuvant such as sodium stearate, sodium carbonate, talc, etc. which improves the releasability from the injection mold of articles injection molded at temperatures at least as low as 93.degree. C.
Copending application Ser. No. 392,221, filed June 25, 1982 describes thermoplastic injection moldable compositions composed of a polyethylene terephthalate, an epoxidized unsaturated triglyceride containing at least one epoxide group and an adjuvant such as sodium stearate, talc, mica, etc. which improves the releasability from the injection mold of articles injection molded at temperatures at least as low as 93.degree. C.
Copending application Ser. No. 401,929, filed July 26, 1982 describes thermoplastic injection moldable compositions composed of a polyethylene terephthalate, an epoxy ester mixture containing at least one monoepoxy aliphatic monocarboxylic acid ester and at least one diepoxy aliphatic monocarboxylic acid ester and an adjuvant, such as sodium stearate, which improves the releasability from the injection mold of articles injection molded at temperatures at least as low as 93.degree. C.